Oscillation translating device



Oct; 31, 1939. V D. T RO 2,177,692

(SSCILLATION TRANSLATING DEVICE Filed June 23, 1937 INVENTOR Michael (I. DiYbrO Patented Oscar, 1939 OSCIILATION TRANSLATING DEVICE Michael I. Di Tom, East Orange, N. 1., assignor to Thomas A. Edison, Incorporated, West, Orange, N. 1., a corporation of New Jersey Application June as, 1931, Serial No. 149,861

13 Claims.

I This invention relates to oscillation translating devices, such as those for the translating or acoustic or electric oscillations into mechanical oscillations, or vibrations.

It is a broad object to provide improved means for reducing or suppressing undesired vibrations of an oscillation translating device.

While no unnecessary limitation thereto is intended, the invention has especial utility, and

has been primarily described, in connection with phonographie apparatus for the recordation of sound-representing oscillations upon a moving record; and an especial aspect of the invention is concerned with the reduction or suppression of certain undesirable resonance eflects', usually of low frequency, in the operation of the recorder.

Properly to understand these effects, it is'flrst desirable to-note the fact that in the operation of impressing or cutting of a moving record by a recorder arranged for movement toward and-away from the record, the greater the depth of penetration in the record of the immediate recordcooperating portion or tool' of the recorder,. the greater is the 'force tending to move this portion or tool out of the record. This is an obedience to the characteristic of restoring force increase accompanying displacement increase, which is the characteristic of a compliance or spring. Ac-

. cordingly the moving record may be considered as characterized by an effective or dynamic complislice (the precise value of which is dependent on zing these e'flects. but they are characterized by Y one or more of the deficiencies of very imperfect action, criticalness of required adjustments, impairment of intended free-movement of the recorder or its portion toward and away fromthe record, and th'elike' It is an object or my invention to reduce or suppress these resonance eflects ,in more emcient manner.

-It is anobiect to. perform such reductionrorc suppression without any requirement for critical adjustment of components of the system. r 5 It is an o i ct to p omsu h reduction or from the following description and the appended claims. 10 In the description reference is had to the ac- I companying drawing, of which- Figure 1 is a partly elevational and partly verti- -.cal cross sectional view of a recorder wherein my invention has been embodied, additional elements 15 of the recording system being shown schematically; Figure 2 is a plan view of the recorder of Figurel;

Figure 3 is a plan view 01' a recorder wherein my 20 invention has been embodied in modified form;

Figure 4 is an end view of therecorder of Figure 3; Figure 5 is a vertical cross-sectional view of a loudspeaker embodying a feature of'my invention; 25

Figure 6 is a vertical view taken along the line -6--8ofFigure5; and

. Figure 1a is a fractional view, of the nature of Figure 1, but illustrating a recorder wherewith my invention has been embodied in a further modified form.

Before describing my invention proper I may first describe a purely typical recorder to which it has been applied and with which it has been illustrated in Figures Hind 2. This recorder 9 1- pears as V, being arranged for the recordation o1 oscillations upon the record R; purely by way of example, this record has been shown as a cylindrlcal one, arranged for rotation by means not herein necessary to show. The recorder has been 40 shown pivoted, for movement toward and away, from the record, to a non-vibratile standardi (for example arranged for slow propulsion transversely or longitudinally of the record by means not herein necessary to show).

The recorder V may comprise a main portion in the form of a frame or casing 3, pivoted to the pivots. 2 in standard I as by the two arms I3 lot the bracket I [secured on the top of the casing at one of the extremities of the latter; and a 50 portion vibratable in accordance with input oscillations and supported by the main portion. By way of example this second portion has been shown as .an electrically vlbratable one, in the term of a piezo-electric bending unit 4 of the so- 5 called bi-morph type--e. g.. comprising two thin crystals secured face-to-face and arranged for simultaneous voltage application in such manner that one crystal expands longitudinally as the other contracts, and vice versa, to result in a transverse (as shown, up and-down) bending of the unit. The unit 4 has been. shown secured at its right-hand extremity in a recessed metal base 3a fastened within the frame or casing 3,

so that its left-hand extremity is available fork up-and-down vibration within the casing in accordance with electric oscillations applied across the electrical leads In; these leads may pass insulatedly out from the unit-for example, to a source of such oscillations comprising an amplifier A fed by microphone M. Secured on the left-hand extremity of the unit 4, and extending outwardly through the suitably apertured bottom of the casing, is a holder 5a, in the bottom of which is held the tool or stylus, 5 adapted to engrave the record.

Somewhat to damp excessive high-frequency peaks of the unit virbation, to render the unit effectively somewhat less fragile, or for allied purposes, it is frequently desirable in recorders of this construction to provide rubber pads or otherdamping means between the unit and the top and bottom, respectively of the casing 3;

such pads have'been fractionally illustrated as l2 in Figure 1. It is to be understood, however,

that such damping function as these perform is the record, the tool will engrave in the record a.

spiral groove. Should the surface level of .the record as presented to the tool vary. slightly up and down with each revolution of the record (as because of a slight out-of-round condition of the record as rotatively supported) the pivoted recorder'and tool are nevertheless free to follow this surface level; and the tool will penetrate, the record surface to a generally constant groove depth predetermined by the record and tool characteristics and by the bias above-mentioned. If at the same time electric oscillations be applied across the unit leads 4a, an oscillatory bending force will be developedin the unit 4, vibrating the tool 5 up and down relative to the. balance of the recorder, or casing 3. The casing. though free of external restraints against movement relative to the record, is largely inhibited from such movement by reason of its own inertia; accordingly, over the greater part of the useful frequency-spectrmn, most of the vibration of the tool relative to the casing .will appear as an absolute vibration of the tool i. e., relative to the record surface-wherefore oscillation representing undulations will be efficiently created in the groove which the tool is engraving. Thevibration of the tool 5 relative to the casing, which gives rise to the desired'absolute tool sonance between (a) a compliance made up of the complianceof the unit 4 and the record compliance, in parallel, and (b) the effective mass, as seen by the record, of the casing with pads I2 and of unit 4 with tool-holder 5a. and tool 5i. e., of the entire recorder. In this frequency region the vibration of the tool 5 relative to theca'sing may attain inordinately high values; attendantly the vibration of each of these elements relative to the record R will become inordinately-high, acom'plex amplitude and phase relation existing between the th'ree vibrations in question. These undue amplitudes of vibration occur whenever the matter to be recorded contains components "lying in the frequency region just mentioned; they cause serious distortion in the recordation, both by seriously exaggerating the amplitudes of these components and by causing hang-over effects .therefrom (i. e., finite continuances of, these components' in the recordation after their termination in the oscillations to be recorded).

' Broadly, there is known-the .use of simple;

damping means for the tool ,or vibratable element of the recorder-such means are comprised,

for examplejin the pads I! which. have "been il-, lustrated in the drawing herein but which formno immediate part of .thepresent invention.

The use of simple damping of the tool or.vibrat'- able. recorder portion, however, is rather ineffective to prevent the unfavorable efiects which are herein specifically considered.

For vibration suppressiongenerally there is termed a dampedvibrationabsorber; this has been described in general terms and at length by. J. P. Den Hart'og on pages103 through 117 of his book entitled Mechanical Vibrations (1934,

known a more elaborate 'system, frequently.

absorber consists of an anti-resonant inechanical system or'structure which is tuned to the frequency of the vibration to be suppressed (or to a frequency slightly lbwerth'an that frequency) andprovided with suitable damping. damped vibration absorber has been disclosed in one instance in connection with vibration translating devices-in United States Letters Patent This No. 2,0 1,948 to Harrison. In this instance, however, not only has it been employed for the suppression of a high frequency resonance occa- 'sioned in reproduction by the actual recordcompliance '(as distinguished from low frequency resonance occasioned in'recordation by the dy-. namic record compliance). but also it has been associated immediately with the record-cooperating tool or vibratable portion of the translating'device, as distinguished from the main portion of the devce. According to the instant inventon, I employ a damped vibration absorber which, in theoretical fundamentala'is of the type disclosed by Den Hartog; I immediately associate it, however,'with the main recorder portion and not with the portion vlbratable by the inputoscillationsand in spite of the apparently continued vibratory freedom of the vibratableportion, the absorber emciently suppresses the objectionable resonance efl'ects above discussed.

For forms of vibration absorber, I ha.v e.de-

vised certain resilient, damped, beam structures. In oneof these; which I have preferred, the structure is of the -clamped-'free" beam,- or

cantilever, variety; this, applied to the described within the clamp may be a respective stop bushing 1. Clampe'd between the tops of the stop bushings l and the clamp 6 isone end of a wide spring 9, which may extend from the clamp in the direction away from the pivots 2, above the casing 3; the other end of this 'spring may be doubly folded over to provide the spring clamp Ill. The anti-resonant structure is completed by the damping means ll, which has been shown terminally held in the clamp 6 and in the spring clamp ID. The beam structures which I utilize, including the one just described, readily permit for this means the employment of a block or slab of one of ,the presently available damping materials of low resiliency and high internal resistance to deformation (1. e., oi low Young's modulus and high internal viscosity). As typical of materials of this character, I may mention reclaimed rubber or, more especially, pliable cellulose nitrate plastic.

The anti-resonant. structure so formed is characterized by a stillness which is made up of that of the spring 9 together with such slight stifiness as the damping slab inherently possesses; by a resistance which is substantially one exhibiting a large sharply peaked value at the frequency of the resonance abovementioned to a characteristic exhibiting two peaks, but each of far lower-and in typical cases quite negligible-amplitudes, and of broader frequency width. The presence of sharp peaks in this admittance characteristic is found to be a measure or the undue vibratory tendencies ofeach component of the complete system; accordingly it will be understood that these tendencies may be vastly reducedby the practice of the invention. And although the anti-resonant structure is attached to the main portion of the recorder, with respect to which .the unit I and toolare vibratable by the input oscillations, the undue vibration of the latter. elements with respect to the main recorder portion is effectively suppressed.

/ It win be understood that 11 the damping means be chosen to have too high a resistance, the reduction olthe undue vibrations will be ineiilcient (even the tuning of-the structure being defeated in the extreme case oi infinite resistance by reason-oi the efle'ctive rigidifying of the structure, rendering it eflectlvely a puremassh On two extremes, however, quite-a wide range or useful resistances, values withinwhich are readily' chosen by test in. any particular case-of, if.

' stant structure, the purelygeneral data presented] in -the Den 'Hartog publication abovementioned.,

' the other han too low a resistance of the damping meansresultiin' replacing an initial highly objectionable resonance with two diflerent freqnency resonances each almost as objectionable as the first. There is'between these desired, by calculations whichapply, to them- As a wholly'illustrative and non-limitativel exampleot dimensioning of components of a'syse tem such as that illustrated, wherein the recorder itself had an eflective mass as seen at the tool of about 4 grams and produced a resonance with the dynamic compliance oi the record It at a frequency of about 200 cycles per second, I may mention the use of a damping slab Ii of the pliable cellulose nitrate plastic identified commercially as Du Pont "Viscoloid'f type X7775, 01' thickness, length andl/ width; and

- of a spring 9, formed immediately thereabout as illustrated, from .003" thick Swedish spring steel.

I may call attention to the fact that the efiectiveness of a structure of the type disclosed may,-

generally speaking, be increased by increasing its width (i. e'., that of the slab H and spring 9)- and that, assuming the structure initially is properly tuned, this width increase need not ordinarily be accompanied by the change of any other dimension. This results from the fact that, although the mass of the structure is obviously changed, the stiffness is simultaneously changed in quite counteracting degree. In the illustrated recorder I have employed a structure width slightly greater than the recorder width-avoiding a still higher structure width only for secondary reasons of objectionable bulk.

Further to aid the eiiectiveness of the structure it is desirable when possible that it extend to a substantially greater distance from the axis of pivots 2 than the distance from that axis of the tool 5; this results in a step-up of the movements of the recorder as those movements tend to appear in the anti-resonant structure. It is alsodeslrable that the beam or cantilever be disposed at least very approximately along .a radial line or plane from the pivoting axis. Both of these desiderata, attaching when the member to which the structure is secured is a pivoted one, are embodied in the system of Figures 1 and 2.

It is to be understood that the direct securing of the anti-resonant structure to the recorder (e. g., to the casing 10' is simply one means of coupling it thereto. and that other coupling 7 means may be employed if desired. Thus in Fig- "ure 101 have illustrated an alternative arrangement, wherein the anti-resonant structure is coupled to the casing 3 through a link system. In this figure the standard i is shown with an upwardly extending arm I. Atthe extremity of this arm are provided pivots 2', and to these is pivoted'a short double armed lever B". To the left-hand extremity of one of the arms of lever 6" is pivotally connected (at P1) the top ex-- trem ity of a link ii, of which the bottom extremity is pivotally connected (at P2) to the bracket l4 (1. e., to one of its arms l3) thus lever G becomes'a secondary element in the system, linked to the primary movable element (e, g.,

' casing l3) for simultaneous movement therewith.

.quite similar (excepting for its position) to the clamp} of Figure 1.. In this clamp are provided a thescrews'! and stop bushings, 1 described in connection with Figure l; and in the clamp is terminally held ,th'e anti-resonant structure 9,lli-'-ll asialso above described.

Inzthis arrangement not only does the link provide a coupling 'means between casing 3 and the anti-fresonantstructure but also, if the distance of P: from 2 is"made large relative to the distanceof P1 from 2" as shown, there is provided a very materialstep-up of the re- ,corder movement as this appearsiuthe damped v case provides some counterbalancing of ill anti-resonant structure. There is also to be noted the fact that the anti-resonant structure the recorder, in distinction to its provision of some additional bias in the arrangement of Figare i. it will of course be understood that the several features of link coupling. motion stepup, and counterbalancing arrangement are available separately or mother combinations than that of all three simultaneously.

I It'will be appreciated that, since the damping slab it does have some apparent stillness as well as mass and resistance, it may in cases .be possible to employ for the anti-resonant structure a beam. formed-of it alone. But latitude of adjustment of resistance relative to reactance I hit damping slab, of the means for retaining the slab values, for optimum effectiveness, is then destroyed. Furthermore many otherwise suitable materials show tendencies to some flow and to rather indefinite restoration characteristics; these tendencies are rendered harmless by the associationwith the unsecured extremity of the against deformation which the spring and spring clamp 9-80, actually provide.

The damped anti-resonant structures which i may utilize are not limited to single cantilever form; they m'ay for example comprise a double cantilever (i. e., centrally clamped beam) structure such as shown in Figures 3 and 4. Herein is seen the clamp it, for example welded to the,

top oi casing t, and having the top and bottom clamping surfaces I6 and I8", respectively. Screws it are provided for drawing these surfaces together, and surrounding each screw between the clamping surfaces I may be a stop bushing ii. The central portion of thin spring i9 is clamped between the top ofthe stop bushings and the top clamping surface l6; each end 4% of the spring is doubly folded over to form a respectivespring clamp 20. In the two spring clamps it are held the ends of a damping slab 28, the center of the slab being clamped between spring is and the bottom clamping surface I6". In respect of tuning and efiectiveness, the double cantilever structure is in general similar to a single cantilever of length equal to the dimension from the center clamp to the extremity, and

of width equal to twice the width, of the double cantilever.

In Figures 3 and 4 I have-illustrated, in association with the damping slabmore particularly, in immediateassociation with spring l9 (e. g.,

with the clamp portions '20 thereofl-locailized masses 22, for example in the form of bars welded or otherwise secured to the spring at the points mentioned. By employing these addi+ tional masses the latitude of adjustmentof reactance and resistance values, for optimum effectiveness at desired frequencies, is still further increased. It will c1,course be understood that such localized. masses may be added in a variety of forms and manners, that the illustration their use is not limited .to the particular double cantilever arrangement of these figures but is available in any of the embodiments of my'ln' vention. 1 c

The damped anti-resonantstructure may also be a .fclamped-clamped beam-i. e., secured at both extremities; in this event the, retention against deformation of the slab of'damping material is inherently fairly well provided, and spring means may be employed or notmore purely in accordance with the tuning requirethereof is n t to be taken as limitative, that.

ments. 3 have illustrated this tom of structure I,

in Figure 5 (without spring) and in- Figure 6 (with spring), applied to a translating device not peculiar to vibration recordation-i. e., applied to a loudspeaker. In these figures the magnetic structure of 'a dynamic loudspeaker appears as 30, energized as by field-coil 3| and having'the annular'gap 32. Extending from infront' into the gap is the annular voice-coil, supporting member 33, carrying the voice-coil 34, and sup-. ported for movement longitudinally of the gap by resilient means schematically indicated as springs 35 .secured to the front of the annular member 33 is the cone or other diaphragm 36; and it will be understood that by the supply of. electric oscillations to the voice-coil 34, the moving system comprising that coil with the member 33 and the diaphragm'will be caused to vibrate in correspondence with those oscillations. In this vibration it is well understood occur-for example, at the frequency of resonance of the mass of the moving system with the compliance of the resilient supporting means 35. For the reduction or suppression of this illustrates the permissible association with the anti-resonant structure of a localized mass 42 for example, a small block of steel welded to the central portion of spring 39.

It will be understood that while my invention has certain special utility with vibration recordare, it may be in cases employed to advantage with phonographic and other vibration reproducers, as well as with otherforms of translating devices. And while I have shown certain, anti-resonant structures in a particular association with an oscillation recorder, and have shown another anti-resonant structure in association with another form of translating device,

I do not intend any unnecessary limitations by virtue of these particular groupings of elements. Rather I undertake to express ,the proper scope of my invention in the appended claims, subject only to such limitations as the state of the art may impose.

I claim:

. 1. In a. system including a tool for-recording oscillations ,upon a moving record: 'a recorder comprising a. tool-carrying portion vibratable in thaa one or more peaks of undue amplitude may I accordance with plural-frequency input oscillations; yajportion supporting said tool-carrying portlon and mounted for movement toward and away from therecord; and a tuned and damped vibration absorber directly coupled to said supporting portion and .efiective as to vibrationsv toward and away from the record." j

2. In a phonographic system including a stylus for co-operating with a moving record: a trans-- lating device comprising a vibratable stylus-carrying portion; a portion supporting said styluscarryingportion and mounted for movement toward and away from the record; and a tuned and v damped vibration absorber directly coupled: to

said supporting portion and elective as to vibrations toward and away from the record.

3. In a phonographic system including a stylus for co-operating'with a moving record: a transtions toward and away from the record, for

damping excessive vibrations of said stylus.

4. In a phonographic system including a stylus for co-operating with a moving-record: a translating device comprising a vibratable stylus-carrying portion; a'portion supporting said styluscarrying portion and mounted for movement relof the translating device with compliance char- 7 ative tothe record; and a damped resilient beam structure, tuned to a.- frequency approximating the frequency of resonance of the efiective mass of the translating device with compliance characterizing the system,yand directly coupled to said supporting portion.

5. In a phonographic system including a stylus for co-operating with a moving record: a translatin'g device comprising a vibratable sty1us-carrying portion; a portion supporting said styluscarrying portion and mounted for movement relative to the record; and a dampedvibration absorber directly coupled to said supporting portion and tuned for eil'ective action in the frequency region .of resonance of the efleetive mass acterizing the system. 6. In a system including a tool for recording oscillations upon a moving record: arec'order comprising a tool-carrying portion vibratable in accordance with plural-frequency input oscilla- 55 means; directly coupled tosaid supporting portions; a portion supporting sa d-tool carrylng portion and mounted for movement toward and away from the record; and a damped antiresonant structure coupled tosaid supporting portion and tuned to a frequency approximating the frequency of resonance of the eflective mass of the recorder with the sum of the dynamic compliance of the record and'the compliance of said tool-carrying portion.-

'7. Ina system including a tool for .recording oscillation'supon a moving record: a'recorder comprising a tool-carrying portion vibratable in accordance with plural-frequency input oscillations; a portion supporting said tool-carrying portion and mounte for movement toward and away from the rec rd;"and tuned anti-resonant tlon, iorsuppressing excessive vibrations of said tool inthe frequency region oi resonance of the carrying portion and mounted for movement toward and away from the record; and tuned anti-resonant means, coupled to said supporting portion in counterweighting arrangement thereto and efiective as to vibrations toward and away from the record, for suppressing excessive vibrations of said stylus in the frequency region of resonance of the'efiective mass of the recorder with compliance characterizing the system.

, 9. In an oscillation-translating system: a movable element forming a portion of said system; and damping means effective on said element comprising a spring secured to and extending from said element, and a slab of damping material of high internal resistance retained in contact with said spring.

. 10. In an oscillation-translating system: a movable element forming a 'portion of said system; anddamping means 'efiective on said element'comprising a spring secured toand extending from said element, and a slab of damp from said element, and meansassociatedwith the .outer end of said slab for retaining said slab against permanent deformation.

12. In an oscillation-translating system: a

movable element forming a portion of said system;- and damping means effective on said eleiment comprising a spring secured to and extending from said element, a slab of damping material of high internal resistance retained in contact with said spring, and a mass associated with a "vibratable portion of said spring.

13'. In an oscillation-translating"system: a movable element forming a portion of said system; and damping means effective on said element comprising a slab of damping material 01 high internal resistance secured to and extending from said element: and a localized mass as- 

